This invention relates to biopesticides, and more particularly to biopesticides that are related to natural sources, including close derivatives and analogs of natural sources.
Pesticides are used to increase the world""s food supply and decrease disease-carrying pests. However, the large-scale use of pesticides has caused widespread concern regarding environmental impact, increased resistance, as well as acute and chronic toxicity to non-target organisms, including man. Many pesticides, particularly the polychlorinated hydrocarbons such as DDT, have generated much controversy because they persist for years in the environment, and have proven harmful to fish and birds of prey. The concern over the buildup of nondegradable pesticides in the soil and in the food chain has prompted the Federal government to ban the production in the United States of many compounds such as DDT, and severely restrict the use of others.
Two widely used classes of pesticides which decompose more rapidly in the environment than polychlorinated hydrocarbons are the organophosphates and carbamates. Many of these compounds, however, are still considered highly toxic and their use is heavily regulated by the Federal government.
The delivery mechanism, i.e., route of exposure, can be by any means known in the art including, but not limited to, fumigation, contact, dietary or aquatic exposure, and/or any combination of these or other known routes of exposure. One commonly used vehicle for eliminating pests is to fumigate. However, because of the need for high volatility in fumigant use, only about 20 chemicals are routinely used, including compounds containing chlorine, bromine and/or phosphorus. Fumigants may also be used in liquid form for injection into the ground to eliminate pests. There is growing concern, however, that persistence in the soil of certain fumigants is harmful to the environment. As a result, commonly used fumigants such as methyl bromide, dichlorvos, ethylene dibromide, chloropicrin, dibromochloropropane, carbon tetrachloride, phosphine, and 1,3-dichloropropene are heavily regulated and their use is severely restricted.
As part of the Federal government""s regulation process, all pesticides must be registered. Since registration can be an extremely time-consuming and very costly process, there has been a marked decrease recently in the registration of new pesticides. This scarcity of new pest control agents has led to concerns that target pests will develop increased resistance to a very limited selection of products. Recently, the government started offering a xe2x80x9cfast-trackxe2x80x9d registration process with the Environmental Protection Agency (EPA) for xe2x80x9cbiopesticidesxe2x80x9d which include both naturally-based pesticides and close derivatives or analogs. Although biopesticides offer a desirable alternative to the highly toxic pesticides, relatively few have been registered to date on the fast-track system.
One possible alternative is to use naturally-based pesticides, i.e., xe2x80x9cbiopesticides.xe2x80x9d It is well-known that plants have built-in natural defenses against insects and other pests, which have evolved over time. Monoterpenoids, for example, are found in the essential oils of many plants, including mints, pine, cedar, citrus, eucalyptus and spices. Monoterpenoids are known to have the ability to aid plants in chemical defense against insects, bacteria, fungi, and even vertebrate herbivores.
As biopesticides, monoterpenoids have been found to have mild insecticidal activity. The structure-activity relationship of monoterpenoids and monoterpenoid derivatives have been studied, as stated in an abstract entitled, xe2x80x9cInsecticidal Properties of Monoterpenoids Against Some Insect Species,xe2x80x9d Sangkyun Lee, et al., Division of Agrochemical of the American Chemical Society, Fall 1993 and in xe2x80x9cToxicity and Neurotoxic Effects of Monoterpenoids in Insects and Earthworms,xe2x80x9d Joel R. Coats, et al., Chapter 20, American Chemical Society, 1991, both of which are hereby incorporated by reference.
Many compounds in this class are also used as flavors or fragrances in foods, cosmetics and pharmaceuticals. Further, there are several monoterpenoids that are commercially available for uses such as flea control on pets and carpets, control of insects on house plants, fumigation of parasitic mites in honey bee colonies, and insect repellency, such as with the citronella candle.
Another class of naturally-based pesticides are the glucosinolates. Within the family Cruciferae (xe2x80x9ccruciferxe2x80x9d), glucosinolates act as natural pesticides in many of the plants. Glucosinolates are a group of over 90 secondary metabolites that occur in only 11 families of dicotyledonous plants, mostly in the family Cruciferae. It has been shown that higher concentrations of glucosinolates correlate with less severe insect attacks. Of interest is the fact that although glucosinolates are reportedly toxic to livestock, they are considered safe for humans. Specifically, within the crucifer family, glucosinolates are found in plants such as cabbages, radishes, turnips, mustard, collard greens, rape, broccoli, kale and crambe (Crambe abyssinica L.). It is the breakdown products of glucosinolates which are responsible for the pungent odor and biting taste of these plants.
Studies concerning effects of monoterpenoids and glucosinolates on insect pests have emphasized chemical ecological functions rather than acute toxicity. For example, glucosinolates have been found to play important roles in aiding certain insect species to identify their proper host plants. Experiments have shown that while too low a concentration of glucosinolates leads to ineffective larval attraction, too great a concentration may actually exert a repellent effect to the cabbage root fly. Others have demonstrated that several glucosinolates have a feeding stimulation effect on the diamond-back moth (Plutella maculipennis Curtis) and the larvae of Pieris brassicae. 
Glucosinolate-containing water extracts from crambe meal showing insect. toxicity in laboratory tests are also known and discussed in xe2x80x9cInsecticidal Toxicities of Glucosinolate-containing Extracts from Crambe Seeds,xe2x80x9d by R. Tsao, et al., 1995 which is hereby incorporated by reference in its entirety. The acute toxicity of these extracts as pesticides, however, is significantly lower than conventional organochlorine or organophosphorus pesticides.
There is ongoing debate as to the risks and benefits posed by various natural versus synthetic pesticides. While it is true that many synthetic pesticides are quite toxic, other synthetic pesticides, such as allethrin and methoprene (which are actually biopesticides), are considered relatively safe. Furthermore, although many natural pesticides are relatively safe, there are clearly others, such as nicotine, which are recognized as being quite hazardous. It is now well-accepted that the biological activity of a chemical is a function of its structure rather than its origin, and the biological properties of a chemical depend on this structure as well as the manner in which the chemical is used. The xe2x80x9csafetyxe2x80x9d of a pesticide, therefore, is dependent not only on the chemical make-up of the product, but also on the actual exposure to the chemical. In many cases, the perceived risk is not consistent with the actual risk.
What is needed, therefore, are new types of pesticides or biopesticides to replace those commercial products which are being banned, restricted or phased out, and so that increasing resistance by target pests can be avoided and/or overcome. Further, the replacement pesticides need to be economical, highly toxic to target pests, and pose less actual risk to the environment and humans as compared to traditional pesticides.
A method for suppressing target pests, comprising exposing the pests to an effective biopesticidal amount of a composition, the composition comprising a carrier and a purified glucosinolate breakdown product having a hydroxyl group attached, wherein a starting material for the purified glucosinolate breakdown product is isolated from a crambe plant or mustard plant, further wherein the target pests are plants, bacteria, fungi or root knot nematodes is disclosed. Methods for suppressing target pests without limitation as to the starting materials are also disclosed wherein the pests are exposed to an effective biopesticidal amount of a composition comprising a carrier and either an analog or a derivative of a purified glucosinolate breakdown product having a hydroxyl group attached. These biopesticides can also be used against plant pests, bacteria, fungi and root knot nematodes.
The present invention provides novel biopesticides that can replace commercial pesticides and biopesticides that have been banned, restricted, or are being phased out, including, but not limited to chloropicrin, dichlorvos and methyl bromide. Many of the biopesticides of the present invention are excellent fumigants, possessing quick action and volatility, while posing less risk than currently used pesticides to humans and the environment.
In one embodiment, the novel biopesticide is a purified form of 4-cyano-3-hydroxy-1-butene (CHB), which is a breakdown product of the principal glucosinolate present in defatted crambe seed meal. Other breakdown products of glucosinolates which have been isolated and purified for use as biopesticides include allyl thiocyanate (ATC), allyl isothiocyanate (AITC) and allyl cyanide (AC).
In a preferred embodiment, an analog of CHB known as 3-cyano-3-hydroxy-1-propene (CHP) is synthesized for use as a biopesticide. CHP is considered a cyanohydrin and has high toxicity or efficacy as a fumigant against pests such as insects and nematodes. Other analogs in the cyanohydrin class are also effective as biopesticides. Examples include the cyanohydrins of simple ketones and aldehydes. Highly effective biopesticides can also be made from isolating the naturally-occurring analogs of CHP which include, but are not limited to dimethyl ketone cyanohydrin (DMK-CNOH) in flax, and methyl ethyl ketone cyanohydrin (MEK-CNOH) in cassava (tapioca).
In an alternative embodiment, derivatives of CHP are produced, including carboxyesters of very small organic acids such as acetic, propionic or propiolic acids. These biopesticides also showed moderate to high efficacy as fumigants.
In yet another alternative embodiment, the derivatives of CHP are carboxyesters made from larger monoterpenoid organic acids such as citronellic acid. These derivatives are essentially xe2x80x9chybridsxe2x80x9d of monoterpenoids and cyanohydrins and also show some pesticidal activity.
The biopesticides of natural origin described above, as well as the biopesticides that are close analogs and derivatives of natural biopesticides, will likely be registered as biopesticides through the EPA""s fast-track registration channels. Such simplified and rapid registration with the Federal government not only saves time for the producer of the pesticides, but decreases the cost of the final product as well. When waste products from the production of plant oils are used as the starting material, such as with the glucosinolates contained in crambe meal, costs can be reduced even further.
The present invention has application with many target pests including, but not limited to, animal pests such as insects, mites, ticks, nematodes, and plant pests such as weed seeds and weeds commonly found in soils. The present invention can also significantly reduce the number of bacteria and fungi commonly found in soils. Furthermore, different formulations, carriers, or routes of exposure can provide for even further uses for suppression of pests. For example, any of these novel pesticides can be used as fumigants in storage bins, buildings, ships, rail cars, fruit trees and any other products or areas, including storage areas, which are prone to attack by pests. Alternatively, toxicity can be by contact, dietary or aquatic exposure.